My employer contested my unemployment but didn’t contest my coworker who was getting 38 hours a week to my 8-16 hours a week during COVID. Had to end up quitting due to school closure . Can they pick and choose which employees to contest ?

I worked for my last job for over 10 years. When COVID hit I had 8-16 hours a week and then school closed down for the year . Ended up having to quit , but was already filing unemployment before that . Started in March and then in July got informed she contested it and I may have to pay back . My co worker started collecting before me with 25-38 hours a week without a child and my boss didn’t contest to her . Can they pick and choose which employees they want to contest ? And why did it take until July for them to notify me she contested when I filed in March ?